it's a free update if you already own it on Steam. so not really a 're-release'

and there's much more than just the new graphics. this article details it: https://www.pcgamer.com/quake-2-remaster-release/

• The original campaign, expansions The Reckoning and Ground Zero, the N64 levels, and the new Call of the Machine episode
• Toggleable graphics upgrades that are stylistically consistent with the original (muzzle flashes, fog, improved lighting, that kind of thing)
• Loads of accessibility features
• Split-screen and online multiplayer
• Co-op, deathmatch, team deathmatch, and CTF, with lots of built-in mutators
• PC/console crossplay
• Support for custom Quake 2 maps, new and old
• Support for new mods, or old ones that have been updated for this 64-bit version
• Improved AI enemies and bots